Definition df-ushgr 25954

Description: Define the class of all undirected simple hypergraphs. An undirected simple hypergraph is a special (non-simple, multiple, multi-) hypergraph for which the edge function e is an injective (one-to-one) function into subsets of the set of vertices v, representing the (one or more) vertices incident to the edge. This definition corresponds to the definition of hypergraphs in section I.1 of [Bollobas] p. 7 (except that the empty set seems to be allowed to be an "edge") or section 1.10 of [Diestel] p. 27, where "E is a subset of [...] the power set of V, that is the set of all subsets of V" resp. "the elements of E are non-empty subsets (of any cardinality) of V". (Contributed by AV, 19-Jan-2020.) (Revised by AV, 8-Oct-2020.)

Assertion

Ref	Expression
df-ushgr	|- USHGraph = { g | [. (Vtx ` g ) / v ]. [. (iEdg ` g ) / e ]. e : dom e -1-1-> ( ~P v \ { (/) } ) }

Distinct variable group:   e, g, v

Detailed syntax breakdown of Definition df-ushgr

Step	Hyp	Ref	Expression
1		cushgr 25952	. 2 class USHGraph
2		ve	. . . . . . . 8 setvar e
3	2	cv 1482	. . . . . . 7 class e
4	3	cdm 5114	. . . . . 6 class dom e
5		vv	. . . . . . . . 9 setvar v
6	5	cv 1482	. . . . . . . 8 class v
7	6	cpw 4158	. . . . . . 7 class ~P v
8		c0 3915	. . . . . . . 8 class (/)
9	8	csn 4177	. . . . . . 7 class { (/) }
10	7, 9	cdif 3571	. . . . . 6 class ( ~P v \ { (/) } )
11	4, 10, 3	wf1 5885	. . . . 5 wff e : dom e -1-1-> ( ~P v \ { (/) } )
12		vg	. . . . . . 7 setvar g
13	12	cv 1482	. . . . . 6 class g
14		ciedg 25875	. . . . . 6 class iEdg
15	13, 14	cfv 5888	. . . . 5 class (iEdg ` g )
16	11, 2, 15	wsbc 3435	. . . 4 wff [. (iEdg ` g ) / e ]. e : dom e -1-1-> ( ~P v \ { (/) } )
17		cvtx 25874	. . . . 5 class Vtx
18	13, 17	cfv 5888	. . . 4 class (Vtx ` g )
19	16, 5, 18	wsbc 3435	. . 3 wff [. (Vtx ` g ) / v ]. [. (iEdg ` g ) / e ]. e : dom e -1-1-> ( ~P v \ { (/) } )
20	19, 12	cab 2608	. 2 class { g | [. (Vtx ` g ) / v ]. [. (iEdg ` g ) / e ]. e : dom e -1-1-> ( ~P v \ { (/) } ) }
21	1, 20	wceq 1483	1 wff USHGraph = { g | [. (Vtx ` g ) / v ]. [. (iEdg ` g ) / e ]. e : dom e -1-1-> ( ~P v \ { (/) } ) }

This definition is referenced by:  isushgr  25956